Electric lamp



1962 TAKAO MINETA 3,059,135

ELECTRIC LAMP Filed May 1, 1961 IN V EN TOR.

BYMW

nT-rbmvsys United States Patent 3,059,135 ELECTRIC LAM]? Takao Mineta, 41 Azabu Zaimokucho, Minato-ku, Tokyo, Japan Filed May 1, 1961, Ser. No. 106,797 Claims priority, application Japan June 7 1960 6 Claims. (Cl. 313113) The present invention relates to an electric lamp for use as a searchlight, a photographic lamp and the like, and is more particularly directed to an electric lamp which is adjustable in focus for obtaining beams of lights condensed, diffused or in parallel.

According to the present invention, there is provided an electric lamp comprising a glass bulb having integral therewith a rearwardly projecting neck portion of cylindrical form and an inner surface coated at the rear half portion thereof with a reflecting layer, a heat-proof and reflecting plate fixedly provided in the bulb at the front end of the neck portion, a movable plate of magnetic substance fitted slidably in the neck portion at the rear of said heat-proof and reflecting plate, a pair of pole rods projecting forwardly from the movable plate slidably extending through the heat-proof and reflecting plate projecting into the interior of the bulb, said rods having at the top ends thereof a filament and being connected electrically with lead-in conductors, and a ring-shaped piece of magnet fitted slidably on the outside of the neck portion of the bulb.

In order that the invention may be easily understood and readily carried into effect, the same will now be explained more particularly, by way of example, with reference to and by the aid of the accompanying drawing, in which:

FIG. 1 is a side view of a preferred form of electric lamp according to the present invention with some parts being broken away,

FIG. 2 is a sectional view taken along the line 1III in FIG. 1, and

FIGURE 3 is a perspective detail view of a portion of the lamp.

Referring to the drawing, numeral 1 denotes a glass bulb of substantially spherical or other forms which has integral therewith a rearwardly projecting neck portion 2 of cylindrical form and an inner surface coated at the rear half portion thereof with a reflecting layer 3. The coated inner surface portion preferably has a semi-circular or parabolic cross-section. A heat-proof and reflecting plate 4, which is made of such a material high in reflection elficiency such as steatite, glass or others and which has its front surface serving as a reflecting mirror, is fixedly mounted in the bulb 1 at the front end of the neck portion 2.

A disk-shaped movable plate 6 is fitted in the neck portion 2 of the bulb 1 at the rear of the heat-proof and reflecting plate 4 so as to be slidable forwardly and rearwardly along the axial direction of the neck portion 2, and a pair of parallel spaced pole rods 7 and 7 projecting forwardly from the movable plate 6 slidably extends through the heat-proof and reflecting plate 4 projecting into the interior of the bulb 1 and are provided at the top ends thereof with a filament 8 bridged therebetween. The movable plate 6 is made of a magnetic substance such as steel or the like, but it is not always necessary that the whole portion thereof is made of such a substance. The plate 6 illustrated in the drawing is so constructed that only the circumferential portion thereof is made of magnetic substance and the inner space thereof is filled with insulating material 9' such as a synthetic resin for lightening the total weight and preventing a short-circuit between the rods 7 and 7.

As in the conventional type of electric lamp, the neck portion 2 has a stem 10 therein at the rear end portion thereof and carries at the rear end thereof a threaded base shell 11 with an eyelet 12. A pair of lead-in conductors 13 and 13 extending forwardly from the stem 16 are connected electrically at their rear ends with the base shell 11 and the eyelet 12, slidably extend through the movable plate 6 for being supported 'at the top ends thereof by the heat-proof and reflecting plate 4 and are connected to their respective pole rods 7 and 7 by a pair of elastic wires 14 and '14.

A ring-shaped piece of magnet 15 is fitted slidably on the outside surface of the neck portion 2 of the bulb '1 so that, in accompaniment with the movement of the piece of magnet 15 forwardly and rearwardly along the axial direction of the neck portion 2, the movable plate 6 is moved within the neck portion 2 and, accordingly, the filament 8 is moved in the bulb 1.

In the use of the lamp of the present invention, by moving the piece of magnet 15 at the outside of the bulb 1, the filament 8 is moved forwardly and rearwardly within the bulb by the same distance as the movement of the piece of magnet 15, whereby the focus of the lamp is adjusted. Important advantages are obtained such as the adjustment of focus which can be performed easily and simply by an outside operation, there is no fear of damaging or injuring the internal mechanisms, and the intensity of light never lessens because there is no obstacle in front of the filament.

What I claim is:

1. An electric lamp comprising a glass bulb having a rearwardly projecting neck portion of cylindrical form integral therewith and an inner surface coated at the rear half portion thereof with a reflecting layer, a heatproof and reflecting plate fixedly mounted in the bulb at the front end of said neck portion, a movable plate of magnetic substance slidably positioned in said neck portion at the rear of said heat-proof and reflecting plate, a pair of pole rods projecting forwardly from said movable plate slidably extending through said heat-proof and reflecting plate projecting into the interior of said bulb, a filament connected to the top end of said rods, lead-in conductors connected to said rods, and a ring-shaped piece of magnet slidably mounted on the outside surface of said neck portion so that, in accompaniment with the movement of said piece of magnet, said movable plate and said filament are moved forwardly and rearwardly for adjusting the focus of the lamp.

2. An electric lamp according to claim 1, wherein said heat-proof and reflecting plate is made of steatite.

3. An electric lamp according to claim 1, wherein said heat-proof and reflecting plate is made of glass.

4-. An electric lamp according to claim 1, wherein said movable plate is wholly made of a magnetic substance.

5. An electric lamp according to claim 1, wherein said movable plate is partly made of a magnetic substance.

6. An electric lamp according to claim 1, wherein said movable plate has a circumferential portion thereof made of a magnetic substance and inner space thereof is filled with an insulating material such as synthetic resin.

Cahill et al. Feb. 5, 1952 Myers Aug. 25, 1959 

